A semiconductor manufacturing apparatus (FIG. 10) using plasma is employed to perform, for example, an etching processing on a semiconductor wafer (hereinafter, referred to as “wafer”) in the course of manufacturing semiconductor products. If particles generated during a manufacturing processing adhere to product wafers, the wafers would be contaminated, resulting in reduction in yield. Thus, a high level of cleanness is required for the semiconductor manufacturing apparatus.
FIG. 10 illustrates a schematic configuration view of a conventional semiconductor manufacturing apparatus 800.
In FIG. 10, the semiconductor manufacturing apparatus 800 includes a processing chamber 810 formed of a cylindrical vessel for performing various processings on a wafer. The processing chamber 810 houses therein a wafer stage for mounting a wafer thereon, and an electrode to which a high voltage is to be applied is buried in the wafer stage. Further, a shower head 811a provided with a number of through holes is disposed at an upper portion of the processing chamber 810, and the shower head 811a serves to introduce an corrosive processing gas for use in a manufacturing processing into the processing chamber 810 via the through holes.
Moreover, a gas supply line formed of a tubular member is connected to the upper portion of the processing chamber 810 to introduce a purge gas into the processing chamber 810. A valve 811 for controlling the flow rate of the purge gas is installed on the gas supply line. Further, a rough pumping line 820 formed of a thin tubular member and a main vacuum pumping line 830 formed of a thick tubular member are coupled to lower portions of the processing chamber 810. The rough pumping line 820 and the main vacuum pumping line 830 are merged into a gas exhaust line.
Installed on the rough pumping line 820 are a dry pump (DP) 822 for exhausting a gas from the processing chamber 810 via the gas exhaust line and a valve 821 for controlling the flow rate of the gas exhausted by the dry pump 822.
Further, on the main vacuum pumping line 830, an automatic pressure controller (APC) 831, an isolation valve (ISO) 832 serving as a gate valve and a turbo molecular pump (TMP) 833 having a gas pumping rate greater than that of the dry pump 822 are installed in that order from the side of the processing chamber 810.
In case of depressurizing the processing chamber 810 of the semiconductor manufacturing apparatus 800 for the manufacturing processing, the processing chamber 810 is first evacuated via the rough pumping line 820 and then, after closing the valve 821, the processing chamber 810 is regulated at a desired vacuum level by means of the main vacuum pumping line 830. When performing an etching processing during the manufacturing process, a high vacuum state is required, and, to maintain the high vacuum level, the vacuum pumping via the main vacuum pumping line 830 is continued during the manufacturing process.
After the completion of the manufacturing processing, a purge gas is supplied into the processing chamber 810 via the gas supply line and is then exhausted externally via the gas exhaust line, during which particles floating within the processing chamber 810 are removed from the processing chamber 810 along with the purge gas, so that the processing chamber 810 is cleaned (see, for example, Japanese Patent Laid-open Application No. H6-056999: Reference 1).
To evaluate the cleanness of the processing chamber 810, there have been made various attempts to monitor particles by using an optical particle monitoring unit (PM) (not shown) which is on the market.
The particle monitoring unit is usually installed between the automatic pressure controller 831 on the main vacuum pumping line 830 and the processing chamber 810, between the automatic pressure controller 831 and the isolation valve 832, or inside the processing chamber 810 to monitor particles discharged from the chamber 810 in real time during the manufacturing processing.
As for the particle monitoring unit, its component, for example, a lens formed of glass tends to be readily corroded by a corrosive processing gas. For example, glass components of the particle monitoring unit would be whitened in about a week after they are first used. Accordingly, the whitened components need to be replaced by new ones or be subject to maintenance work. Consequently, costs of the semiconductor manufacturing apparatus 800 are increased, while its operating time decreases. As a solution to this problem, by installing the particle monitoring unit on the rough pumping line 820, it is possible to prevent the corrosion of the glass components of the particle monitoring unit.
Since it is difficult to monitor the particles that are moving at a high speed of, for example, 20 m/sec, there has been proposed a technique for allowing the particle monitoring unit to monitor the particles by controlling the flow cross-sectional area of a gas that flows through the gas exhaust line such as the vacuum main pumping line 830 formed of a thick tubular member, to thereby improve the probability for detecting the particles (see, for example, Japanese Patent Laid-open Application No. H11-304688: Reference 2).
Further, the semiconductor manufacturing apparatus 800 in FIG. 10 further includes a transparent window member (not shown) formed of quartz glass (SiO2). The window member is installed to face the processing chamber 810 and serves as a window for introducing, for example, a microwave into the processing chamber 810.
If the quartz glass forming the window member is exposed to fluorine-based plasma atmosphere, the silicon (Si) atom of SiO2 would react with an active molecule such as a fluorine radical contained in the fluorine-based plasma and then volatilize as silicon fluoride (SiF4), thereby contaminating the wafer or depositing on the surface of the window member to blur it (i.e., deterioration occurs).
Typically, for the purpose of preventing such deterioration, the quart glass is heated. Further, to suppress the deterioration of the window member, there has been also proposed a window member formed of a member made by dispersing a first phase of quartz into a second phase of alumina (Al2O3) (see, for example, U.S. Pat. No. 6,797,110: Reference 3). Furthermore, for parts such as bell jar and a focus ring which are used in the processing chamber other than the window member, there has been an amorphous material of silica and alumina formed by melting silica (SiO2) containing aluminum (Al) (see, for example, Japanese Patent Laid-open Application No. 2003-292337: Reference 4). All of these techniques aim at improving the resistance to the fluorine-based plasma or the active molecules by forming a preset member containing aluminum therein.
However, References 1 and 2 disclose merely the technique of monitoring particles that are moving along with the gas exhausted from the processing chamber 810, but none of them discloses or suggests a technique of monitoring deposits adhered on the inner wall of the processing chamber 810.
The deposits might come apart from the inner wall of the processing chamber 810 during the manufacturing process and the like, resulting in a contamination of the wafer. Therefore, it is required to evaluate the cleanness of the processing chamber 801 more precisely by monitoring the deposits on the chamber wall as well.
In addition, when heating the quartz glass of the window member to prevent the deterioration thereof, a defect may be caused in an electric circuit disposed within the semiconductor manufacturing apparatus 800 or deterioration of a laser unit may be accelerated.
Furthermore, with regard to the above techniques for allowing a member to contain aluminum therein, since aluminum atoms are dispersed in silica or quartz, the surface of the member cannot exhibit plasma resistance or resistance to active molecules efficiently, so that the frequency of replacing the member increases. As a result, the time required for the replacement work increases, which in turn results in deterioration in the productivity of the semiconductor manufacturing apparatus 800. Moreover, due to the increase of costs for the replacements, overall costs of the semiconductor manufacturing apparatus 800 rises. Further, to prevent the deterioration of the productivity of the semiconductor manufacturing apparatus 800 and increase of the costs, the window member for use in the particle monitoring apparatus connected to, for example, the main vacuum pumping line also needs to meet the condition of low frequency of replacement.